linux - Golang csv 在 linux 上写空

Question

我在 linux 上写 csv 文件时遇到问题，使用完全相同的代码，它在 windows 上工作，但在 linux(Centos7)上没有任何内容写入文件:

package main

import (
    "os"
    "fmt"
    "encoding/csv"
)

var data = [][]string{
    {"1","2","3","4","5"},
    {"a","b","c","d","f"},
}


func main() {
    filename := "example.csv"
    fp,e := os.OpenFile(filename, os.O_CREATE|os.O_APPEND, os.ModePerm)
    if nil != e {
        fmt.Printf("Open file '%s' failed: %s\n", filename, e)
        os.Exit(1)
    }
    defer fp.Close()
    w := csv.NewWriter(fp)
    defer w.Flush()
    for _,l := range data {
        if e := w.Write(l); nil != e {
            fmt.Printf("Write csv failed: %s\n",e)
            os.Exit(1)
        }
    }
    fmt.Println("Done.")
}

Answer 1

Golang 规范描述 OpenFile :

OpenFile is the generalized open call; most users will use Open or Create instead. It opens the named file with specified flag (O_RDONLY etc.) and perm (before umask), if applicable. If successful, methods on the returned File can be used for I/O. If there is an error, it will be of type *PathError.

您缺少写入使用 OpenFile 函数创建的文件的标志，这就是打开文件进行写入或读取但未向 csv 写入任何内容的原因。

package main

import (
    "encoding/csv"
    "fmt"
    "os"
)

var data = [][]string{
    {"1", "2", "3", "4", "5"},
    {"a", "b", "c", "d", "f"},
}

func main() {
    filename := "example.csv"
    fp, e := os.OpenFile(filename, os.O_CREATE|os.O_APPEND|os.O_WRONLY, os.ModePerm)
    if nil != e {
        fmt.Printf("Open file '%s' failed: %s\n", filename, e)
        os.Exit(1)
    }
    defer fp.Close()
    w := csv.NewWriter(fp)
    defer w.Flush()
    for _, l := range data {
        if e := w.Write(l); nil != e {
            fmt.Printf("Write csv failed: %s\n", e)
            os.Exit(1)
        }
    }
    fmt.Println("Done.")
}

Playground Example

标志在源代码中详细说明 os/file.go :

// Flags to OpenFile wrapping those of the underlying system. Not all

// flags may be implemented on a given system.

const (
    // Exactly one of O_RDONLY, O_WRONLY, or O_RDWR must be specified.
    O_RDONLY int = syscall.O_RDONLY // open the file read-only.
    O_WRONLY int = syscall.O_WRONLY // open the file write-only.
    O_RDWR   int = syscall.O_RDWR   // open the file read-write.
    // The remaining values may be or'ed in to control behavior.
    O_APPEND int = syscall.O_APPEND // append data to the file when writing.
    O_CREATE int = syscall.O_CREAT  // create a new file if none exists.
    O_EXCL   int = syscall.O_EXCL   // used with O_CREATE, file must not exist.
    O_SYNC   int = syscall.O_SYNC   // open for synchronous I/O.
    O_TRUNC  int = syscall.O_TRUNC  // if possible, truncate file when opened.

)